Aspinall unit operations update

Aspinall Unit

From email from Reclamation (Erik Knight):

The April 15th forecast for the April – July unregulated inflow volume to Blue Mesa Reservoir is 850,000 acre-feet. This is 126% of the 30 year average. Snowpack in the Upper Gunnison Basin is currently 124% of average. Blue Mesa Reservoir current content is 623,000 acre-feet which is 75% of full. Current elevation is 7495.3 ft. Maximum content at Blue Mesa Reservoir is 829,500 acre-feet at an elevation of 7519.4 ft.

Black Canyon Water Right

The peak flow and shoulder flow components of the Black Canyon Water Right will be determined by the May 1 forecast of the April – July unregulated inflow volume to Blue Mesa Reservoir. If the May 1 forecast is equal to the current forecast of 850,000 acre-feet of runoff volume, the peak flow target will be equal to 6,427 cfs for a duration of 24 hours. The shoulder flow target will be 831 cfs, for the period between May 1 and July 25. The point of measurement of flows to satisfy the Black Canyon Water Right is the Gunnison River below Gunnison Tunnel streamgage at the upstream boundary of Black Canyon of the Gunnison National Park.

Aspinall Unit Operations ROD

Pursuant to the Aspinall Unit Operations Record of Decision (ROD), the peak flow and duration flow targets in the lower Gunnison River, as measured at the Whitewater gage, will be determined by the forecast of the April – July unregulated inflow volume to Blue Mesa Reservoir and the hydrologic year type. At the time of the spring operation, if the forecast is equal to the current forecast of 850,000 acre-feet of runoff volume, the hydrologic year type will be set as Moderately Wet. Under a Moderately Wet year the peak flow target will be 14,350 cfs and the duration target at this flow will be 10 days. The duration target for the half bankfull flow of 8,070 cfs will be 40 days.

Projected Spring Operations

During spring operations, releases from the Aspinall Unit will be made in an attempt to match the peak flow of the North Fork of the Gunnison River to maximize the potential of meeting the desired peak at the Whitewater gage, while simultaneously meeting the Black Canyon Water Right peak flow amount. The magnitude of release necessary to meet the desired peak at the Whitewater gage will be dependent on the flow contribution from the North Fork of the Gunnison River and other tributaries downstream from the Aspinall Unit. Current projections for spring peak operations show that flows in the Gunnison River through the Black Canyon could be over 9,000 cfs for 10 days in order to achieve the desired peak flow and duration at Whitewater. If actual flows on the North Fork of the Gunnison River are less than currently projected, flows through the Black Canyon could be even higher. With this runoff forecast and corresponding downstream targets, Blue Mesa Reservoir is currently projected to fill to an elevation of around 7507 feet with an approximate peak content of 719,000 acre-feet.

Aspinall Unit operations update

Morrow Point Dam spilling June 2014 via USBR

From email from Reclamation (Erik Knight):

The April 1st forecast for the April – July unregulated inflow volume to Blue Mesa Reservoir is 930,000 acre-feet. This is 138% of the 30 year average. Snowpack in the Upper Gunnison Basin is currently 147% of average. Blue Mesa Reservoir current content is 582,000 acre-feet which is 70% of full. Current elevation is 7490.1 ft. Maximum content at Blue Mesa Reservoir is 829,500 acre-feet at an elevation of 7519.4 ft.

Black Canyon Water Right

The peak flow and shoulder flow components of the Black Canyon Water Right will be determined by the May 1 forecast of the April – July unregulated inflow volume to Blue Mesa Reservoir. If the May 1 forecast is equal to the current forecast of 930,000 acre-feet of runoff volume, the peak flow target will be equal to 6,575 cfs for a duration of 24 hours. The shoulder flow target will be 921 cfs, for the period between May 1 and July 25. The point of measurement of flows to satisfy the Black Canyon Water Right is the Gunnison River below Gunnison Tunnel streamgage at the upstream boundary of Black Canyon of the Gunnison National Park.

Aspinall Unit Operations ROD

Pursuant to the Aspinall Unit Operations Record of Decision (ROD), the peak flow and duration flow targets in the lower Gunnison River, as measured at the Whitewater gage, will be determined by the forecast of the April – July unregulated inflow volume to Blue Mesa Reservoir and the hydrologic year type. At the time of the spring operation, if the forecast is equal to the current forecast of 930,000 acre-feet of runoff volume, the hydrologic year type will be set as Moderately Wet. Under a Moderately Wet year the peak flow target will be 14,350 cfs and the duration target at this flow will be 10 days. The duration target for the half bankfull flow of 8,070 cfs will be 40 days.

Projected Spring Operations

During spring operations, releases from the Aspinall Unit will be made in an attempt to match the peak flow of the North Fork of the Gunnison River to maximize the potential of meeting the desired peak at the Whitewater gage, while simultaneously meeting the Black Canyon Water Right peak flow amount. The magnitude of release necessary to meet the desired peak at the Whitewater gage will be dependent on the flow contribution from the North Fork of the Gunnison River and other tributaries downstream from the Aspinall Unit. Current projections for spring peak operations show that flows in the Gunnison River through the Black Canyon could be over 8,500 cfs for 10 days in order to achieve the desired peak flow and duration at Whitewater. If actual flows on the North Fork of the Gunnison River are less than currently projected, flows through the Black Canyon could be even higher. With this runoff forecast and corresponding downstream targets, Blue Mesa Reservoir is currently projected to fill to an elevation of around 7518 feet with an approximate peak content of 816,000 acre-feet.

Aspinall Unit Spring streamflow forecasts

Aspinall Unit
Aspinall Unit

From email from Reclamation (Erik Knight):

The February 15th forecast for the April – July unregulated inflow volume to Blue Mesa Reservoir is 970,000 acre-feet. This is 144% of the 30 year average. Snowpack in the Upper Gunnison Basin is currently 166% of average. Blue Mesa Reservoir current content is 576,000 acre-feet which is 69% of full. Current elevation is 7489.3 ft. Maximum content at Blue Mesa Reservoir is 829,500 acre-feet at an elevation of 7519.4 ft.

Black Canyon Water Right

The peak flow and shoulder flow components of the Black Canyon Water Right will be determined by the May 1 forecast of the April – July unregulated inflow volume to Blue Mesa Reservoir. If the May 1 forecast is equal to the current forecast of 970,000 acre-feet of runoff volume, the peak flow target will be equal to 7,158 cfs for a duration of 24 hours. The shoulder flow target will be 966 cfs, for the period between May 1 and July 25. The point of measurement of flows to satisfy the Black Canyon Water Right is the Gunnison River below Gunnison Tunnel streamgage at the upstream boundary of Black Canyon of the Gunnison National Park.

Aspinall Unit Operations ROD

Pursuant to the Aspinall Unit Operations Record of Decision (ROD), the peak flow and duration flow targets in the lower Gunnison River, as measured at the Whitewater gage, will be determined by the forecast of the April – July unregulated inflow volume to Blue Mesa Reservoir and the hydrologic year type. At the time of the spring operation, if the forecast is equal to the current forecast of 970,000 acre-feet of runoff volume, the hydrologic year type will be set as Moderately Wet. Under a Moderately Wet year the peak flow target will be 14,350 cfs and the duration target at this flow will be 10 days. The duration target for the half bankfull flow of 8,070 cfs will be 40 days.

Projected Spring Operations

During spring operations, releases from the Aspinall Unit will be made in an attempt to match the peak flow of the North Fork of the Gunnison River to maximize the potential of meeting the desired peak at the Whitewater gage, while simultaneously meeting the Black Canyon Water Right peak flow amount. The magnitude of release necessary to meet the desired peak at the Whitewater gage will be dependent on the flow contribution from the North Fork of the Gunnison River and other tributaries downstream from the Aspinall Unit. Current projections for spring peak operations show that flows in the Gunnison River through the Black Canyon could be over 8,000 cfs for 10 days in order to achieve the desired peak flow and duration at Whitewater. If actual flows on the North Fork of the Gunnison River are less than currently projected, flows through the Black Canyon could be even higher. With this runoff forecast and corresponding downstream targets, Blue Mesa Reservoir is currently projected to fill to an elevation of around 7515 feet with an approximate peak content of 790,000 acre-feet.

@usbr: Aspinall Unit operations update: 600 CFS in Black Canyon

Fog-filled Black Canyon via the National Park Service
Fog-filled Black Canyon via the National Park Service

From email from the US Bureau of Reclamation (Erik Knight):

Releases from Crystal Dam will be increased from 600 cfs to 1200 cfs between Monday, February 6th and Tuesday, February 7th. This increase is in response to the high runoff forecast for Blue Mesa Reservoir this spring. The latest runoff forecast predicts 925,000 af of runoff to Blue Mesa Reservoir between April and July, which is 137% of average. The current content of Blue Mesa Reservoir is 586,000 acre-feet which is 71% full.

Flows in the lower Gunnison River are currently above the baseflow target of 1050 cfs. Flows are expected to remain above the baseflow target for the foreseeable future.

Pursuant to the Aspinall Unit Operations Record of Decision (ROD), the baseflow target in the lower Gunnison River, as measured at the Whitewater gage, is 1050 cfs for February through May.

Currently, diversions into the Gunnison Tunnel are at zero and flows in the Gunnison River through the Black Canyon are around 600 cfs. After this release change Gunnison Tunnel diversions will still be at zero and flows in the Gunnison River through the Black Canyon should be around 1200 cfs. Current flow information is obtained from provisional data that may undergo revision subsequent to review.

Aspinall Unit operations meeting, Thursday, January 19, 2017

Aspinall Unit
Aspinall Unit

From email from Reclamation (Erik Knight):

The next Aspinall Operations meeting will be held this Thursday, January 19th at the Holiday Inn Express in Montrose CO. The meeting will start at 1 PM.

Aspinall Unit operations update: Gunnison Tunnel turning off, 600 cfs in Black Canyon

Fog-filled Black Canyon via the National Park Service
Fog-filled Black Canyon via the National Park Service

From email from Reclamation (Erik Knight):

Releases from Crystal Dam will be decreased from 1500 cfs to 600 cfs on Tuesday, November 1st. This reduction will follow the shutdown of diversions to the Gunnison Tunnel. Release reductions will be coordinated with Gunnison Tunnel diversion reductions throughout the morning of November 1st. River flows downstream may fluctuate during the shutdown period but flows should steady out at the current level by the afternoon. The current content of Blue Mesa Reservoir is 610,000 acre-feet which is 73% full.

Flows in the lower Gunnison River are currently above the baseflow target of 1050 cfs. Flows are expected to remain above the baseflow target for the foreseeable future.

Pursuant to the Aspinall Unit Operations Record of Decision (ROD), the baseflow target in the lower Gunnison River, as measured at the Whitewater gage, is 1050 cfs for November through December.

Currently, diversions into the Gunnison Tunnel are around 900 cfs and flows in the Gunnison River through the Black Canyon are around 600 cfs. After this release change Gunnison Tunnel diversions will be at zero and flows in the Gunnison River through the Black Canyon should still be around 600 cfs. Current flow information is obtained from provisional data that may undergo revision subsequent to review.

@USBR: The next Aspinall Unit operations meeting is Thursday #ColoradoRiver #COriver

Aspinall Unit dams
Aspinall Unit dams

From email from Reclamation (Eric Knight):

The next Aspinall Operations meeting will be held this Thursday, August 18th at the Elk Creek Visitor Center at Blue Mesa Reservoir. Start time is 1 PM.